Solar system

A team from MIT has tested a prototype of a new solar power system that consists of a 12ft-wide dish made from a frame of thin, aluminium tubing and strips of mirror.

Attached to the end of an aluminium tube that rises from the centre of the dish is a black coil of tubing that has water running through it. When the dish is pointing directly at the sun, the water in the coil flashes immediately into steam.

Spencer Ahrens, who has just received his master's in mechanical engineering from MIT, hopes that the company he and his colleagues have founded - RawSolar - will produce such dishes by the thousands.

He said they could be set up in huge arrays to provide steam for industrial processing, or for heating or cooling buildings, as well as to hook up to steam turbines and generate electricity.

Once in mass production, such arrays should pay for themselves within a couple of years with the energy they produce.

'This is actually the most efficient solar collector in existence,' said Doug Wood, an inventor based in Washington state who patented key parts of the dish's design - the rights to which he has signed over to the MIT team.

The MIT engineers have made significant improvements to Wood's original design to make it a practical and competitive energy producer. 'They really have simplified this and made it user-friendly, so anybody can build it,' he added.

One of the keys to making an inexpensive design was something Wood discovered by accident as he built a variety of solar dishes over the years: smaller really is better.

Unlike many technologies where economies of scale dictate large sizes, a smaller dish requires so much less support structure that it ends up costing only a third as much, for a given collecting area.

'I've looked for years at a variety of solar approaches and this is the cheapest I've seen,' added David Pell, MIT Sloan School of Management lecturer.

Matt Ritter, Doug Wood, Spencer Ahrens and Micah Sze mount one of the mirror panels in place